Blackberry Jam
Ingredients
Directions
Prepare the fruit
Pick the blackberries and mash them through a colander with a potato masher, discarding the white seeds.
Weigh the mashed fruit and place it in a pot over heat.
Cook the jam
When it begins to boil, stir in the baking soda and boil for about 45 minutes, skimming regularly.
Add the sugar and continue boiling until the mixture thickens and looks like it will be stiff when cold.
Seal the jam tightly in glass jars.
Transcribed from a scanned cookbook and modernised for today's kitchens. Where the book gave no heat or time, or said "a moderate oven", the temperatures and times here may be modern equivalents rather than the book's own figures.
Explore the science
What each ingredient does
- Blackberries
- Provide the fruit body, flavour and natural pectin that help the jam set.
- White sugar
- Sweetens the jam and, with boiling, helps it thicken and set as it cools.
- Baking soda
- Raises the pH of the fruit, which can alter colour and softens the cooking acidity.
The step that matters
Boiling until the jam thickens. Jam sets when enough sugar and pectin are concentrated by boiling. Undercooked jam stays runny, while overcooking can make it stiff and dull. Judge by the cold-set test described in the step.
“What each ingredient does” and “The step that matters” were written by Claude from this recipe’s own method and reviewed in samples by CompKitchen.
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